Electrical and structural characterization of metal-oxide-semiconductor capacitors with silicon rich oxide

Metal-oxide-semiconductor capacitors in which the gate oxide has been replaced with a silicon rich oxide (SRO) film sandwiched between two thin SiO2 layers are presented and investigated by transmission electron microscopy and electrical measurements. The grain size distribution and the amount of crystallized silicon remaining in SRO after annealing have been studied by transmission electron microscopy, whereas the charge trapping and the charge transport through the dots in the SRO layer have been extensively investigated by electrical measurements. Furthermore, a model, which explains the electrical behavior of such SRO capacitors, is presented and discussed. © 2001 American Institute of Physics

Memory effects in MOS capacitors with silicon quantum dots

To form crystalline Si dots embedded in SiO2, we have deposited thin films of silicon-rich oxide (SRO) by plasma-enhanced chemical vapor deposition of SiH4 and O2. Then the materials have been annealed in N2 ambient at temperatures between 950°C and 1100°C. Under such processing, the supersaturation of Si in the amorphous SRO film produces the formation of crystalline Si dots embedded in SiO2. The narrow dot size distributions, analyzed by transmission electron microscopy, are characterized by average grain radii and standard deviations down to about 1 nm. The memory functions of such structures has been investigated in MOS capacitors with a SRO film sandwiched between two thin SiO2 layers as insulator and with an n+ polycrystalline silicon gate. The operations of write and storage are clearly detected by measurements of hysteresis in capacitance-voltage characteristics. A model which explains both the occurence of steady-state conduction through the SiO2/SRO/SiO2 stack at a relatively low voltage and the shift of flat-band voltage is presented and discussed. © 2001 Elsevier Science B.V. All rights reserved

Washing effectiveness assessment of different cleaners on a small-scale multistage compressor

Suspended micrometric particles are always present in the air swallowed by gas turbines. These solid particles can overpass the filters of heavy-duty gas turbines and deposit onto the internal surfaces of the compressor, leading to the overtime reduction of the machine performances, and, as a result, to the fuel consumption augmentation. A widely employed method to slow down the engine degradation is to wash the engine frequently. Over the years, the washing techniques have been continuously improved in order to reach the best compromise between low fluid consumption and high washing capabilities. In this work, an experimental campaign has been carried out to estimate the washing effectiveness on a multistage axial-flow compressor fouled with micrometric soot particles. The cleaning fluids tested in the present work were demineralized water and two cleaners provided by ZOK International Group ltd: A commercial cleaner available on the market (ZOK 27), and a new, under development, environmentally-sensitive formula. The fluids have been tested employing three droplet size distributions (with mean diameters of 20 mm, 50 mm, and 100 mm). The washing effectiveness has been assessed through image post-processing techniques by analyzing the pictures of the stator vanes and rotor blades taken in fouled and washed conditions. From the present investigation, two results arise. The finest droplets show a greater capability to remove soot deposits showing how, when the washing operation takes place during quasi-idle operating condition, the turbulent-driven motion spread smaller particles on a wider blade region. The second results is the demonstration how a environmentally-sensitive chemical formula allows the obtainment of good results in terms removal capability for the same amount of product. This finding could help the plant manager to operate the gas turbine with less constraints in terms of cost and rules

Memory effects in MOS capacitors with silicon rich oxide insulators

To form crystalline Si dots embedded in SiO2, we have deposited thin films of silicon rich oxide (SRO) by plasma-enhanced chemical vapor deposition of SiH4 and O2. Then the materials were annealed in N2 ambient at temperatures between 950 and 1100 °C. Under such processing, the supersaturation of Si in the amorphous SRO film produces the formation of crystalline Si dots embedded in SiO2. The narrow dot size distributions, analyzed by transmission electron microscopy, are characterized by average grain radii and standard deviations down to about 1 nm. The memory function of such structures has been investigated in metal-oxide-semiconductor (MOS) capacitors with a SRO film sandwiched between two thin SiO2 layers as insulator and with an n+ polycrystalline silicon gate. The operations of write and storage are clearly detected by measurements of hysteresis in capacitance-voltage characteristics and they have been studied as a function of bias

Nanocrystal MOS with silicon-rich oxide

By electrical measurements we investigate the charge trapping and the charge transport in MOS capacitors in which the gate oxide has been replaced with a silicon rich oxide (SRO) film sandwiched between two thin SiO2 layers

Numerical analysis of particle deposition in an aircraft engine compressor cascade

Solid particles dispersed in the air represent a real hazard for gas turbines in both heavy-duty and aero-propulsion applications. Particles impacting the inner surfaces of the machine can stick to such surfaces or erode them. The geometry modifications related to such occurrences entail aerodynamic surface degradation. As the severity of the problem increases, the performance reduction can increase, demanding engine shut-down and off-line washing or refurbishing. Numerical modeling is one of the techniques employed for understanding and predicting the particle deposition problem. Multiple numerical studies investigated the influences of these phenomena. However, the basic challenge of modeling the particle wall-interaction with sufficient accuracy remains. In this work, a cascade exposed to a particle-laden flow is numerically investigated. The numerical analysis is devoted to investigate a test rig designed to be representative of aircraft engine compressor blading and exposed to an accelerated deposition process. Firstly, the relation between flow structures and particle trajectory is investigated. Then, a computational analysis is carried out considering different particle-wall interaction models of varying complexity levels (e.g. pure adhesion, presence of humidity or the influence of surface roughness) in order to identify advantages and disadvantages of each model and their ability to include different phenomena. The results are discussed by taking into account measurement data from a cascade test rig. The deviation between experimental data and the investigated model is evaluated, showing the increasing reliability that derives from successive model refinement. This work is proposed to be a test case for the numerical analyses of compressor fouling applications and a first step towards a general physical based particle-wall interaction model

Memory effects in single-electron nanostructures

We investigate the memory function at room temperature in devices based on quantum dots. By Low Pressure Chemical Vapour Deposition (LPCVD) we deposited Si dots embedded in SiO2. On these devices flat band voltage shifts were well detected at low write voltages for write times of the order of milliseconds, and furthermore, a plateau in the flat band voltage shift, maybe consequence of Coulomb blockdale, was observed

Residual crystalline silicon phase in silicon-rich-oxide films subjected to high temperature annealing

Structural properties of silicon rich oxide films (SRO) have been investigated by means of micro-Raman spectroscopy and transmission electron microscopy (TEM). The layers were deposited by plasma enhanced chemical vapor deposition using different SiH4/O2 gas mixtures. The Raman spectra of the as-deposited SRO films are dominated by a broad band in the region 400-500 cm-1 typical of a highly disordered silicon network. After annealing at temperatures above 1000\ub0C in N2, the formation of silicon nanocrystals is observed both in the Raman spectra and in the TEM images. However, most of the precipitated silicon does not crystallize and assumes an amorphous microstructure. \ua9 2002 The Electrochemical Society. All rights reserved